Engine systems are used in a variety of applications such a vehicle applications. Some engine systems include a two-stage turbocharger system, which includes a low pressure turbocharger and a high pressure turbocharger. A turbocharger is a turbine-driven, forced-induction compressor that improves the efficiency of an engine by delivering greater air flow into the engine cylinders. Turbochargers are powered by the exhaust gases of the engine. A turbocharger typically includes a turbine and a compressor connected by an axle. Exhaust gases from the engine cause the turbine wheel to rotate, which drives the compressor. The compressor compresses ambient air and delivers the air to the intake manifold of the engine at higher pressure which results in greater air flow to the engine cylinders. The additional air makes it possible to add more fuel, which increases the power and torque output of the engine.
A problem with conventional two-stage turbocharger systems is that at certain high mass flow conditions, the high pressure compressor can act like a constriction. When the speed limit is reached on the high-pressure (HP) turbine, the flow through the HP turbine is bypassed. This reduces the efficiency of the HP turbine, which in turn reduces the ability of the HP compressor to efficiently compress the charge.
Accordingly, what is needed is an improved turbocharger system that does not restrict air flow to the engine. The turbocharger system should be cost-effective. The present invention addresses such a need.